Thermographic television systems utilize the infrared electromagnetic radiation emanating from the surface of objects or bodies to form a video image. Various infrared video signals are usually displayed either in various shades of grey or in different colours, depending on whether the television display monitor provides black and white or colour displays. Consequently the surface flux variations are easily discernable by the viewer. The regions between various isotherms are normally given a distinct grey shade or colour.
Thermographic television systems have been used in applications such as crop surveying from earth satellites, in medicine, etc. Particularly in the latter application, sources of heat such as cancer nodules located deep in the body are sometimes too difficult to detect and locate distinctly and accurately due to diffusion of heat through layers of body tissue. In particular, there may be small but distinctive asymmetry of heat generation localities on opposite sides of the body, which are very difficult to discern, but which may be important.